Artifacts dating back billions of years have been attributed to the Preservers, further strengthening the theory that they and the ancient humanoids are one and the same. (TOS novel: Federation, Preserver)

The original Preservers were the last members of the race of Ancient Progenitors that seeded humanoid life throughout the Milky Way. Over the eons, they watched over the development of their progeny species, leaving many artifacts behind. Eventually, they faded from the galaxy -- through interbreeding with their "genetic descendants," war, plague and other causes -- but not before passing the mantle on to the more advanced of those races. The Vhorani were one, and they spread throughout the near side of the galaxy, seeding life on Vulcan, Mintaka III and other worlds. Milennia later, they would be remembered in the Romulan myths of Vorta Vor. (Star Trek: Pendragon: "Starkindler", et. al)

Other offshoots of the Preservers included the Anu'anshee, and the group known as the Aegis. The Aegis would take special interest in the people of Earth, and established a line of "Watchmen" to observe and defend the human race. Akharin was descended from this line. Among the Preserver artifacts they left on Earth was one that would eventually become known as the Holy Grail. (PDN: "The Once and Future King, Parts I & II")

In the 5th century, a group of Celts were also transplanted from Earth, though that may have been directly caused by "Merlin". (PDN: "The Once and Future King, Part I")

The influence of the Preservers even spread as far as the Delta Quadrant, where they visited the Ocampa homeworld before the time of the Caretaker. They transplanted several thousand Ocampa to an isolated planet in the Beta Quadrant, hidden by a nebula near the galactic barrier. Eventually the Beta Quadrant Ocampa would develop longer lifespans, and increased psionic capabilities. (PDN: "Sanctuary")

In the mid-24th century, several Preserver artifacts were brought to Enclave J-12 on Titan, where they were studied by young Timothy Sinclair, under the guidance of Dr. Robert Blaisdell. Sinclair grew to become a "Preserver chaser," and when he left the Enclave in 2355, he followed their trail towards the galactic rim. He would later write several papers on the Preservers' influence on the galaxy, most notably When the Stars Changed: The Truth Behind Common Myth, which was published after his disappearance in 2386. (PDN: "Air and Darkness", "Odyssey, Parts I & II", "Camelot's Ashes", "Another Time, Another Place", "Above the Wrecks of Time", "The Hand of God", et. al)

Sinclair's son, Tyler, likewise became a Preserver chaser, and continued his father's work. (PDN: "True North", "Air and Darkness", "The Kraken", "Starkindler", "Above the Wrecks of Time")

The Preservers took dozens of beings from various worlds and various time periods at the moments of their death. These people -- "The Chosen" -- were cryogenically frozen, and awakened in 2455, five years after a great cataclysm decimated the galaxy, in the hopes of restoring civilization.